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While working for a broadcasting/networking integration gig, we designed, assembled and field-terminated thousands of copper and fibre runs from 1/2 ft to footb

While working for a broadcasting/networking integration gig, we designed, assembled and field-terminated thousands of copper and fibre runs from 1/2 ft to football field lengths. The amount of time required to terminate a copper cable in the field is seconds, and felt a bit like art. Something about the way it reliably reacted was magical and felt "strong." Terminating or splicing a fibre cable felt like wrestling a snake covered in melted crayons, and the failure rate was significantly higher across the board. And it wasn't just workmanship, but quality of product, terminating environment, available equipment, misuse by future operators etc. That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Though, maybe part of our willingness to push fibre came from knowing that most purchasers would in 1-2 years call us back in to replace the rack terminations with copper :)

zamadatix 4mo ago
There are 2 very different main types of "copper" in this context. Each can break down into more specific subcategories but they have a relatively common general behavior with their primary type. First there is the BASE-T RJ45 stuff, which it sounds like you might have been working with. At 10G or higher speeds this get relatively power hungry and is not really an advantage over fiber unless you are also delivering PoE or are trying to reuse existing cabling. This type (DAC) is a special type of pre-made cable assembly which eschews much of the advanced signalling/conversion logic. The upside is the power usage is low (often even lower than fiber) and the cost is dirt cheap. The downside is the lengths are much more limited and it's intended to be preterminated SFP-to-SFP (or the like) cable assemblies instead of modular patching/custom built. There is indeed a latency difference, usually DAC < fiber < BASE-T, but they are all within a few microseconds (not milliseconds) of each other so you really have to be pressed to care about it (to the point you're looking at specialized low latency switches and paying extra to lay things out in a way which minimizes the number of L2 hops rather than the cost).
- myself248 4mo ago
  > it's intended to be preterminated SFP-to-SFP I wonder why nobody's making field-terminatable DACs for custom lengths. If you've torn one down, they're not exactly complicated inside. If they existed, would people buy them?
  - jeffrallen 4mo ago
    Nope. For production, you want to reduce risk and variation. DACs are already available in about 5 sizes up to the max 7m length, why would you terminate any other size in the field?
    - iso1631 4mo ago
      I did spec a couple of 7m dacs a few months ago to run between two adjacent bays, but normally for more than 2m I'll just drop a SM sfp and run a preterminated fibre cable. In the field its the armoured fibre on a reel, 100m, 200m, 500m etc, with opticon connectors, or some normal cat5 typically for APs
      - bobdvb 4mo ago
        Some network guys I know prefer fibre even within the rack, just because they don't want the weight and the obstructions in the rack. Apparently more than once the weight of the DACs and the bulk of the cable bundle has caused a problem with NICs. Personally that surprised me, but I can see where they're coming from.
        wmf 4mo ago
        Support brackets would be 10x cheaper than fiber.
        iso1631 4mo ago
        The fibre and sfps are a tiny price of the entire solution DACs will be cheaper than fibre in a bay, but between neighbouring bays about the same. A 7m passive 40g qsfp dac is £80. A pair of multimode 40g is £66 and 7m multimode cable is £10. A 2m dac is £28, so fibre is 3 times the price.
throw0101c 4mo ago
> That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Copper bundles get real thick, real fast: I ran an OneFS cluster for many years, and we had >50 nodes, and all the cables (each node dual-connected) ran to two central switches for backend replications. Rat's nest. I was very happy when Isilon started officially supporting active optical cable (AOC) on the backend. Really helped with airflow and keeping things tidy.
Aurornis 4mo ago
> The amount of time required to terminate a copper cable in the field is seconds, This article is about Direct Attach Copper (DAC) cables which are not something you can field terminate. They use twinax copper and have special modules on the end. You are thinking about standard RJ45 terminated cabling for 1GBASE-T or 10GBASE-T, which is a different. > That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Direct Attach Copper has slightly lower latency than fiber, but the difference is negligible. Both have significantly better latency than 10GBASE-T through twisted pair cabling.
- SV_BubbleTime 4mo ago
  Yes, thanks. It was confusing me for a second because no, no almost one is terminating twinax in the server room. I had IT company recommend to me a bunch of fiber cables for a cleanup I was doing. They had about 20 or 30 laser modules we would need, and however much fiber. When they asked why I planned on doing copper, I told him because each run is three fucking feet. I’m not sure if they just didn’t realize that’s not what fiber is for or they didn’t know that DAC existed.
  - Aurornis 4mo ago
    Many people don’t know about DAC. Like the comment above I think they see the word copper and assume it means the twisted pair they’re familiar with.
    - simulator5g 4mo ago
      There's also a common misconception that copper means slow. Because when you have internet from a copper cable in the US, it usually sucks.
runjake 4mo ago
Couple points: 1. The copper cables discussed in the article are not field terminable. And if they were, they'd be a pain in the ass. 2. Terminating fiber used to be a pain, but is now pretty easy with the right tools, fuser, and someone with basic training. Even cheap fusers do the job with very low failure rates. They now have so-called "knuckle draggers" terminating fiber.
RantyDave 4mo ago
Were you not into SDI for broadcast stuff?
- jweather 4mo ago
  Pretty sure that's the copper they're talking about.
dark-star 4mo ago
I'm pretty sure you didn't design, assemble and field-terminate DAC cables. These are not regular RJ45 or DB25 serial cables, which you can assemble in the field. I have never heard of the possibility to field-assemble DAC cables. Usually that's when you switch to fiber
stephen_g 4mo ago
How much of that was terminating vs splicing for the optical fibre? I have not done the actual hands on work of splicing but have specified fibre runs a couple of times and all the guidance I have seen is that for reliability you want to always splice on good-quality, factory-terminated pigtails because field terminated connectors are (so I've read) very unreliable. When possible we've just run pre-terminated cables so we don't have to get somebody in to splice and that's been really reliable.

zamadatix 4mo ago

There are 2 very different main types of "copper" in this context. Each can break down into more specific subcategories but they have a relatively common general behavior with their primary type. First there is the BASE-T RJ45 stuff, which it sounds like you might have been working with. At 10G or higher speeds this get relatively power hungry and is not really an advantage over fiber unless you are also delivering PoE or are trying to reuse existing cabling. This type (DAC) is a special type of pre-made cable assembly which eschews much of the advanced signalling/conversion logic. The upside is the power usage is low (often even lower than fiber) and the cost is dirt cheap. The downside is the lengths are much more limited and it's intended to be preterminated SFP-to-SFP (or the like) cable assemblies instead of modular patching/custom built. There is indeed a latency difference, usually DAC < fiber < BASE-T, but they are all within a few microseconds (not milliseconds) of each other so you really have to be pressed to care about it (to the point you're looking at specialized low latency switches and paying extra to lay things out in a way which minimizes the number of L2 hops rather than the cost).

myself248 4mo ago
> it's intended to be preterminated SFP-to-SFP I wonder why nobody's making field-terminatable DACs for custom lengths. If you've torn one down, they're not exactly complicated inside. If they existed, would people buy them?
- jeffrallen 4mo ago
  Nope. For production, you want to reduce risk and variation. DACs are already available in about 5 sizes up to the max 7m length, why would you terminate any other size in the field?
  - iso1631 4mo ago
    I did spec a couple of 7m dacs a few months ago to run between two adjacent bays, but normally for more than 2m I'll just drop a SM sfp and run a preterminated fibre cable. In the field its the armoured fibre on a reel, 100m, 200m, 500m etc, with opticon connectors, or some normal cat5 typically for APs
    - bobdvb 4mo ago
      Some network guys I know prefer fibre even within the rack, just because they don't want the weight and the obstructions in the rack. Apparently more than once the weight of the DACs and the bulk of the cable bundle has caused a problem with NICs. Personally that surprised me, but I can see where they're coming from.
      - wmf 4mo ago
        Support brackets would be 10x cheaper than fiber.
        iso1631 4mo ago
        The fibre and sfps are a tiny price of the entire solution DACs will be cheaper than fibre in a bay, but between neighbouring bays about the same. A 7m passive 40g qsfp dac is £80. A pair of multimode 40g is £66 and 7m multimode cable is £10. A 2m dac is £28, so fibre is 3 times the price.

throw0101c 4mo ago

> That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Copper bundles get real thick, real fast: I ran an OneFS cluster for many years, and we had >50 nodes, and all the cables (each node dual-connected) ran to two central switches for backend replications. Rat's nest. I was very happy when Isilon started officially supporting active optical cable (AOC) on the backend. Really helped with airflow and keeping things tidy.

Aurornis 4mo ago

> The amount of time required to terminate a copper cable in the field is seconds, This article is about Direct Attach Copper (DAC) cables which are not something you can field terminate. They use twinax copper and have special modules on the end. You are thinking about standard RJ45 terminated cabling for 1GBASE-T or 10GBASE-T, which is a different. > That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Direct Attach Copper has slightly lower latency than fiber, but the difference is negligible. Both have significantly better latency than 10GBASE-T through twisted pair cabling.

SV_BubbleTime 4mo ago
Yes, thanks. It was confusing me for a second because no, no almost one is terminating twinax in the server room. I had IT company recommend to me a bunch of fiber cables for a cleanup I was doing. They had about 20 or 30 laser modules we would need, and however much fiber. When they asked why I planned on doing copper, I told him because each run is three fucking feet. I’m not sure if they just didn’t realize that’s not what fiber is for or they didn’t know that DAC existed.
- Aurornis 4mo ago
  Many people don’t know about DAC. Like the comment above I think they see the word copper and assume it means the twisted pair they’re familiar with.
  - simulator5g 4mo ago
    There's also a common misconception that copper means slow. Because when you have internet from a copper cable in the US, it usually sucks.

runjake 4mo ago

Couple points: 1. The copper cables discussed in the article are not field terminable. And if they were, they'd be a pain in the ass. 2. Terminating fiber used to be a pain, but is now pretty easy with the right tools, fuser, and someone with basic training. Even cheap fusers do the job with very low failure rates. They now have so-called "knuckle draggers" terminating fiber.

RantyDave 4mo ago

Were you not into SDI for broadcast stuff?

jweather 4mo ago
Pretty sure that's the copper they're talking about.

dark-star 4mo ago

I'm pretty sure you didn't design, assemble and field-terminate DAC cables. These are not regular RJ45 or DB25 serial cables, which you can assemble in the field. I have never heard of the possibility to field-assemble DAC cables. Usually that's when you switch to fiber

stephen_g 4mo ago

How much of that was terminating vs splicing for the optical fibre? I have not done the actual hands on work of splicing but have specified fibre runs a couple of times and all the guidance I have seen is that for reliability you want to always splice on good-quality, factory-terminated pigtails because field terminated connectors are (so I've read) very unreliable. When possible we've just run pre-terminated cables so we don't have to get somebody in to splice and that's been really reliable.